High-frequency transmission



July 3, 1928. 1,675,890

J. c. GABRIEL HIGH FREQUENCY TRANSMISSION Filed Dec. 29, 1923 2 Sheets-Sheet l Angular Roiah'on.

% h Coupling //71 /7/0f.' J /m 6. am/e/ by July 3, 1928. 1,675,890

J. c. GABRIEL HIGH FREQUENCY TRANSMI SS ION iiled Dec. 29, 1925 2 Sheets$heet 2 Patented \July 3, 1928.

UNITED STATES PATENT OFFICE.

' JOHN C. GABRIEL, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

HIGH-FREQUENCY TRANSMISSION,

Application filed December 29, 1923. Serial No. 683299.

This invention relates to radio transmission and reception systems, and more particularly to systems adapted to be used for ship-to-shore communication.

An object of the invention'is to provide for carrying on communication at the wave lengths and frequencies best adapted to radio telephony and also at the customary commercial wave length and frequency.

More specifically, an object is to provide for two-way communication by alternately transmitting on one wave length and receiving on another without changing the tuning of'the set for each separate operation.

A further object is to provide for a more effective and convenient tuning of radio apparatus.

A further object is to provide for a more construction of high frequency oscillation generators by modifying their circuit arrangement so as to reduce insulation difiiculties.

Ditficulty has been experienced heretofore in ship-to-shore communication in that two sets were necessary; one for use with radio telephony at such wave lengths and frequencies best suited for that type of service and one for radio telegraphy over the commercial wave length of 600 meters. The present invention overcomes this difiiculty by providing'means whereby transmission and reception of telephone signals can be carried out and also transmission of telephone signals and reception of telegraph signals can be accomplished with minimum tuning of the set for each separate operation.

This invention comprises a transmitting circuit including a microphone, a source of high frequency waves and modulating means; a receiving circuit including a first detector, an intermediate frequency selective circuit, and a second detector. A switch is provided whereby in one position duplex operation may be effected by combining energy of the incoming and outgoing carrier wave frequencies to produce an intermediate frequency wave which is selected by the in termediate frequency selective circuit. In another position of the switch the receiving circuit is normally connected to the antenna. When the operator wishes to transmit a key is opened to connect the transmitting circuit to and disconnect the receivmg circuit from the antenna. Operation of the switch is all that is necessary to change the entire circuit from a condition adapted for onetype of transmission to a condition adapted for the other.

In addition to the foregoing it is possible to switch into circuit a separate localoscil-' lator to beat down the incoming waves to an intermediate frequency instead of utilizmg energy, of the outgoing waves for the purpose. I hen so operating both the transmitting and receiving circuits are connected to the antenna.

It is also possible to receive by means of a single stage of detection only; for this purpose the telephone receivers may be plugged into the circuit at a point preceding the intermediate frequency detector.

Auxiliary features are coils for tuning the high frequency selective-circuit of the receiver havin such characteristics that the coupling vanes practically linearly with the angle of rotation of the control dial over a range of 180.

Certain complete systems embodying the invention are described hereinafter. However, the invention is not limited to a particular embodiment but may be embodied in other constructions. Certain parts of the described apparatus may be utilized in other systems. The novel features which are considered to reside in this invention consist of certain combinations and arrangements of parts and methods which are defined in the claims.

In the drawings, Fig. 1 represents a circuit diagram of a system embodying the various features of the invention.

Fig. 2 shows the arrangement of coupling coils whereby linear variation of coupling with angular rotation is secured.

Fig. 3 represents a more detailed arrangement of the same coils and their associated parts.

Fig. 4 represents a view of the coils shown in Fig. 3 taken at right angles to Fig. 3 on the line H and looking in the direction of the arrows;

Fig. 5 represents an alternative coupling arrangement whereby several of the advantages of the arrangement of Figs. 2, 3 and 4 ma be secured by simpler means.

F ig. 6 consists of a light curve showing) the variation of coupling with rotation with ordinary variometers or coupling coils, and a heavy straight line curve showing the linear vaniation secured by the present arrangements.

' Fig. 1 represents a combined transmitting and receiving system for ship-to-shore radio communication. A transmitting circuit T includes microphone 2, source of high frequency waves '3 together with modulating and amplifying apparatus 1 of any conventional type which functions to modulate waves from the source 3 in accordance with waves from the microphone source 2. Modulated waves are impressed upon the aerial 10 through a circuit including grounded inductance coil 4, variable inductance 5, capacity 6 and an insulated portion 9 of a contact arm 7 which is held to the left by spring 16.

Switch 11 is of the double throw type, making contact with contacts 12 and 13 for different methods of operation. In the left hand position of switch 11, a trap circuit consisting of condenser 18 and high frequency coil 17 is connected by the upper contact 12 and switch 11 into the receiving circuit, constituting a path in shunt to the aerial with respect to the transmitter cir-. cuit.

By means of switch 11, contacts 13 and release of push buttonor key 19, relay 14 is energized by a source of direct current 15 thereby throwing contact arm 7 to the right,

this being the position opposite that in which it is normally held by spring 16. When the, contact arm is inthis position, i. e. to the right and with switch 21 closed on its lower contacts, incoming waves traverse a circuit including variable capacity 20, left hand contact 22, inductance 24, right hand blade of double throw switch 21, corresponding contact 23, inductance 25, and to ground through switch 21. Current is induced in coil 26 by coils 24 and .25. The waves are thus impressed on the high .frequency vacuum tube detector 27 because of the coupling between the coils 2425, and 26.

- High frequency oscillations roduced by vacuum tube oscillator 28may e impressed upon the grid of detector 27 through inductance coils 33, switch 34, transformer 35 and inductance coils 36 to beat with the incoming waves thereby producing an intermediate frequency wave. 4

Oscillator 28 may be of any well known type, for example, as disclosed in Fig. 3 (e) page 69 of the Proceedings of the In-- stitute of Radio Engineers, vol. 6, No. 2, April, 1918.

value, which constitutes a low frequency amplifier.

The output circuit ofthe high-frequency detector 27 is connected to the primary of transformer 30, the secondary of which is quency wave to detector 37. Variable condenser 38, connected between inductances 26 and 36, cooperates with the inductances to form atuned circuit. Circuit 83 comprises a condenser shunted by a grid leak resistance for the detector 27.

In the case of continuous wave'telegraph reception, oscillations from oscillator 39 may be impressed upon detector 37 which operates to combine them with the interme diate frequency waves to produce an audible note which is amplified by low frequency amplifier 41 and received in the receiver 42.

Oscillator 39 is of the type disclosed in the patent to Heising 1,442,147, January 16, 1923, with a modified structural arrangement. Instead of coil 43 being divided into two parts with a variable condenser connected therebetween the coil consists of a continuous winding with positive lead 48 from battery 58 connected to the midpoint of coil 43. Condenser 44 is'connected in parallel relation to coil 43 to complete the tuned circuit. Condenser 49 is located between'the source 59 of filament current and the positive lead 48 to allow a high frequency path from the mid-point of coil 43 to the filament without allowing direct curthe difiiculty of securing good insulation,-

between the points at which the condenser formerly was connected, is overcome. Condenser 45 is inserted in the grid circuit to cooperate with a resistance 46, of high grid leak path for the oscillator.

tions to the detector 37 through coil 43, coil 51 and transformer 40.

'Switch 50 controls the filament supply circuit of oscillator 39, 84 being the corresponding switch for oscillator 28. Circuit Switch 47-cbntrols the supply of oscillai 52, comprising a condenser shunted by a leak resistance is included in the grid circuit of the detector 37. Condenser 55, in shunt to the primary winding of the input transformer, forms a by-pass for keeping the waves of intermediate frequency from reaching the low frequencyamplifier forms a by-pass for to keep waves of the inter- 'mediate frequency, in shunt to the primary Winding of the input transformer for the Low frequency oscillations produced by the detector 37 are impressed upon the low frequency amplifier by means of transformer 53, across the secondary of which a resistance 54 is shunted. Amplified low frequency oscillations are received by receiver 42 through the transformer 57 having a high resistance 56 connected in series with its primary. Sources of direct current 58 and 59 supply current for the operation of oscillators 28 and 39. They also supply current to the space paths and filaments of the tubes 27, 29, 37 and 41. Battery 60 supplies polarizing potential to the grid 0t tube 29 and battery 61 impresses a polarizing )otential upon the grid of tube 41.

I reception is to be accomplished with the use of a single detector only, the received waves may be by-passed around the intermediate frequency detector, selecting circuit, and amplifier by means of a double ended cord circuit 84. Low frequency waves pro- 30 duced by the detector 27 are then transferred directly to the amplifier 41 and are supplied to the telephones 42.

Coupling coils 24 and are shielded by shield 81, constructed of non-magnetic con- 5 duct-ive material such as zinc and coils 26 and 36 are shielded by shield 82 of the same material.

Fig. 2 shows the construction of coils 24, 25 and 26. Terminals 21, 22 and 23 correspond to similarly numbered switch contacts shown in Fig. 1. Each of the coils 24. 25 and 26 are built in such manner that half of each is of the solenoid type and the other half is of the figure 8 type. By figure 8 type of coil is meant the general type illustrated in U.- S. Patent 1,367,- 734, Feb. 8, 1921, to Curtis. Coils 24 and 25 are stationary while 26 revolves.

A characteristic feature of the construction shown in Fig. 2 is that the variation of coupling between coils 24 and 26, and be- }tween the series connected coils 24 and 25 and 26, is practically linear over a range of 180. This variation of coupling is proportional to the angle of rotation of the movable coil 26, as shown in Fig. 6; wherein the line a represents the coupling variation in the present arrangement and curve 1) the coupling variation in the case of 5 previously known coils. Leads 66 and 67 .of the movable coil 26 pass through the hollow shaft 65 to spring contacts 64 and 63, respectively.

Fig. 3 shows the arrangement of the tuning coils 24, 25 and 26 with respect to their container and also with respect to the panel of the radio set. Coils 24 and 25 are fastened rigidly to casing 90 and coil 26 may be rotated by means of the knob 73 to which 0 the calibrated dial 72 is attached. Hollow shaft is mounted in bearings and 71. Metallic strip 68 and 69 on the inside of cylindrical shell 76 furnish means for completing the circuit with spring contacts 63 5 and 64. The coils, in combination with the shell, are surrounded by a container which is fastened 'to'the panel 77.

Fig. 4 represents the structure of the figure 8 type sections, showing the manner in which they are wound and the means for holding two of the coils rigid. The shield 74 is split at to prevent the. shield from forming a completely closed circuit. Shielding strips 87 are provided to complete the shield, strips 87 being separated from shield 74 by strips 86 of insulating material.

In Fig. 5 an alternative arrangement of tuning coils is shown. Coil 78 is fastened rigidly to the base 80 and coil 79 can be moved from a position having its winding parallel to winding of coil 78 to a posit-ion in which its winding is at right angles to the winding of coil 78. Coil 79 is mounted on a pivotal bearing which is located adjaeent its periphery at a point remote from coil 78. Because of this method of mounting, the coupling between the coils varies gradually as the coil 79 is adjusted thereby providing for an accurate setting for small coupling effects. The variation of coupling is not exactly linear from zero to maximum, but is a fair approximation thereto.

0pemt-z'0n.'lhis system may be used to transmit and receive in accordance with several different methods.

Full Juptem-In one method, the switch 11 is thrown to the left to disconnect the push button 19 and the relay 14, and to connect the trap circuit, comprising inductance 17 and capacity 18, in series with the receiving circuit. The trap circuit is tuned to eliminate practically all of the high frequency oscillations used in transmitting, but a small amount of the energy of the transmitted frequency is passed therethrough and is combined with the received oscillations in the detector 27 to produce an intermediate frequency signal modulated wave.

For transmitting in normal ship-to-shore telephone work a high frequency wave, for example, 800,000 cycles is used. This wave is modulated in accordance with speech waves in the transmitting apparatus T and is radiated from antenna 10.

For full duplex operation the contact bar 7 is in the left hand position and switch 21 is in engagement with contacts 22. Incoming waves of a frequency, for example, of 750,000 cycles incident upon the antenna 10, pass through portion 9 of contact bar 7, condenser 6, contact 12, switch 11, trap circuit 1718, portion 8 of contact bar 7 and the tuned circuit comprising capacity 20 and inductance 24.

By means of the tuned circuit, comprising capacity 38 and inductance 26, both the incoming waves and the outgoing oscillations passed through the trap circuit are impressed upon the detector 27. The two frequencies are combined by the detector 'to produce an intermediate frequency of,

in this case, 50,000 cycles. This intermediate frequency is in turn amplified by intermediate frequency amplifier 29, then impressed.

upon the device 37 in whichthey are detected to yield the audible modulating or speech frequency currents, which are amplified by low frequency amplifier 41, and supplied to the receiver 42.

Second metkodFuZZ dwpZem.-Switch 11 is thrown to the left, as before, and switch 21 in the up position. The local oscillator 28 may be adjusted to produce an intermediate frequency wave different than that produced by the incoming and outgoing carrier Waves. Thus for example, the out-' passed through the trap circuit, is combined with the incoming wave .to produce a beat frequency of 50,000 cycles and is also combined with the oscillations supplied by the oscillator 28 to produce a wave of 30,000 cycles, both of which frequencies are suppressed by the intermediate frequency tuned circuits.

Push button operation-In accordance with another method, using the same frequencies, the switch 11 is thrown to the right,

to connect the push button 19 and relay 14 into the circuit, switch 21 being thrown to engage contacts 23. For transmitting the button 19 is held open, the relay 14 is deene'rgized and transmission is carried out in the manner described 111 connection with 'the previous system, with the exception that the trap circuit 17, 18 is disconnected. For receiving, however, the push button 19 is released, and relay 14 is energized, thereby attracting the horizontal portion of the contact arm 7, thus causing the bar to make contact with the points on the right. In-

coming waves now pass through capacity 20, inductances 24 and 25 and are impressed upon tuned circuit 02. In this case, the oscillator 28 furnishes the oscillations to beat with the incoming waves. These oscillations are supplied to the tuned circuit 62 by means of transformer 36. From this point the method of receiving is similar to that previously described.

If the operator wishes to transmit telephone messages, using the wave length and frequency selected for this purpose, but at the same time desires to receive messages, over the commercial wave length of 600 meters, i. e. at 500,000 cycles; he uses this latter method, by tuning the oscillator 28 to some,

frequency for example, 550,000 cycles, which,

by combining with the incoming Wave, pro- I duces an-intermediate frequency of 50,000

messages. For reception on the commercial wave length of 600 metersv (500,000 cycles) the loop circuit 20, 24 must be removed from thecrrcuit asits reactance would not permit tumng to the desired frequency. By throwng-switch 21 to the down position, i. e. mto engagement with the contacts 23, the condenser 20, inductance 24 and an additional inductance 25 are connected in series. If the inductance 25' is of the correct value the set will be tuned to receive upon 600 meters, if not of the right value some slight readjustment of at least one of the circuit elements, for example, condenser 20, may be necessary. Thus the requirement for listening in on 600 meters may be complied with. If it is necessary to respond to some message received on a 600 meter wavelength the transmitting circuit maybe tuned to transmit on that wave length. For receiving continuous undamped wave signals, heterodyn mg may be accomplished by connecting in the oscillator 28. p

- This system may also be used to receive telegraph messages on unmodulated or continuous waves. Incoming telegraph waves are received by the antenna and impressed upon the high frequency detector 27 along with oscillations from oscillator 28 to produce an intermediate frequency wave, in the manner described in the last two methods.

The intermediate frequency wave may be taken as before as being 50,000 cycles. Oscillator 39 is tuned to some lower frequency, for example, 49,000 cycles to beat withintermediate frequency. Both free quencies are then impressed upon the detector 37 by means of transformer 40 and tuned circuits 31 and 32. The resultant 1,000 cycle waves are amplified by low frequency amplifier 41 and are supplied to receiver 42.

As an alternative arrangement, the oscil-' -lator"'39 may be used as a test oscillator for the transmission system. This is especially advantageous in the, method wherein oscillations to beat with the incoming waves are supplied to the receiving circuit by the transmission oscillator through the trap circuit. Knowin the frequency of the incoming waves and the intermediate frequency desired, the oscillator 39 is tuned to this intermediate frequency. Ifan audible'note is produced in the receiving device 42, the transmission oscillator is not supplying oscillations of the frequency desired for transmission. The transmission oscillator may be tuned to the desired frequency by adjusting its frequency determining circuit until the note is no longer heard in the receiver 42.

lfii) It will, of course, be understood by those skilled in the art that the devices herein shown and described are only illustrative of particular means that may be employed for specific purposes, and that the details of construction and the relative arrangement and location of parts may be materially varied from those set forth, without departing from the spirit of the invention and its scope of the invention, which is defined in the appended claims.

What is claimed is:

1. A radio system comprising a transmitter circuit and a receiver circuit including tuning elements, an antenna, a switch adapt ed in one position to connect said circuits to said antenna, whereby oscillations of the frequency used for transmission maybe supplied to said receiver circuit to be combined therein with the incoming wave to produce an intermediate frequency wave; a second switch adapted to control the connection of the tuning elements of said receiver circuit, whereby, upon actuation of said antenna switch to a second position and movement of said second switch to a corresponding position, the receiver circuit is conditioned to receive a wave of widely different frequency from the wave received before actuation of said switches.

2. A radio telephone system comprising an antenna, a transmitter and a receiver normally connected directly to said antenna so that incoming and outgoing waves are supplied to said receiver and are therein combined to produce an intermediate frequency signal modulated wave, and switching means for converting said system to a system including a transmit-receive relay for controlling the connection of said transmitter and said receiver to said antenna and for reception on a widely different wave length from that used when said transmitter and receiver are directly connected to said antenna.-

3. The method of establishing the frequency of the transmitter of a two-way radio communication circuit which comprises connccting a testing generator of a desired intermediate frequency to the receiver circuit, producing a wave of beat frequency by combining the outgoing and incoming carrier waves, combining the wave of beat frequency with the wave from the testing generator, and varying the frequency of the transmitted wave until the beat frequency wave and the testing generator wave coincide.

4. A radio receiver for use with a transmitter for duplex radio communication by combining incoming and outgoin carrier Waves to produce intermediate frequency waves which comprises a cord circuit and jacks for by-passing detected waves around the intermediate frequency selecting and detecting circuits, in combination with switches for cutting the transmitter circuit off from the antenna and connecting the receiving circuit to the antenna.

5. In a radio, communication system an aerial circuit means for connecting said aerial to ground through two paths, one of said aths comprising under one condition a condenser in shunt to a coil having a figure 8 portion and a solenoid portion, ,a switch for connecting said coil and condenser in series with each other and with another coil of the same type, a third coil of the same type operatively coupled to said first mentioned coil under said one condition and operatively coupled to both of said first mentioned coils when said coils are connected in series. v

In witness whereof, I hereunto subscr' my name this 26 day of December A. 1):,

JOHN C. GABRIEL. 

